Magnetically guided catheter

ABSTRACT

A catheter includes a flexible tubing having a proximal end and a distal end. The catheter also includes an electrode assembly attached to the distal end of the flexible tubing and having a first magnet therein. The electrode assembly further includes an electrically conductive tip electrode and an electrically nonconductive coupler which is connected between the tip electrode and the distal end of the flexible tubing. The coupler and the tip electrode are coupled by an interlocking connection. The catheter also includes a second magnet spaced from the electrode assembly along a longitudinal axis of the tubing. The first magnet and the second magnet are responsive to an external magnetic field to selectively position and guide the electrode assembly within a body of a patient.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/532,164, filed 25 Jun. 2012 (the '164 application), now issued asU.S. Pat. No. 8,715,279, which is a continuation of U.S. applicationSer. No. 12/167,736, filed 3 Jul. 2008 (the '736 application), nowissued as U.S. Pat. No. 8,206,404, which claims the benefit of U.S.provisional application No. 60/947,791, filed 3 Jul. 2007 (the '791application). The '164 application, the '736 application and the '791application are hereby incorporated by reference as though fully setforth herein.

BACKGROUND OF THE INVENTION

This invention relates generally to medical instruments, and, morespecifically, to a navigable catheter device positionable within a bodyof a patient using an externally applied magnetic field.

Catheters are flexible, tubular devices that are widely used byphysicians performing medical procedures to gain access into interiorregions of the body. Careful and precise positioning of the catheterswithin the body is important to successfully completing such medicalprocedures. This is particularly so when catheters are used to produceemissions of energy within the body during tissue ablation procedures.Conventionally, positioning of such catheters was accomplished withmechanically steerable devices. More recently, magnetically navigablecatheter devices have been developed that may be navigated with anexternally applied magnetic field. Such catheter devices can be complexin their construction, and therefore are difficult to manufacture andrelatively expensive to produce.

Magnetic stereotactic systems have been developed that are particularlyadvantageous for positioning of catheters, as well as other devices,into areas of the body that were previously inaccessible. Such systemsutilize computer controlled superconducting coils to generate specificmagnetic fields or gradients to move a catheter that is provided withmagnetic components responsive to such magnetic fields. The magneticfields and gradients are generated to precisely control the position ofthe catheter within the patient's body. Once correctly positioned,physicians may operate the catheter, for example, to ablate tissue toclear a passage in the body. Specifically, such stereotactic systemsmonitor the position of a tip of the catheter in response to the appliedmagnetic fields of the superconducting coils, and using well establishedfeedback and control algorithms the catheter tip may be guided to andpositioned in a desired location within the patient's body.

The magnetic response of the catheter can be a limitation on the precisecontrol of a catheter when used with such magnetic guidance systems.Improvements in catheters utilized with magnetic guidance and controlsystems, such as stereotactic systems, are desired. Specifically, a lowcost, yet high performance magnetically guided catheter is desirable.

BRIEF DESCRIPTION OF THE INVENTION

In various embodiments, magnetic guided catheters are disclosed that aremanufacturable at relatively low cost while providing high performancewhen used with, for example, magnetic stereotactic systems.

In one embodiment, a catheter is provided that includes a flexibletubing having a proximal end and a distal end. The catheter alsoincludes an electrode assembly attached to the distal end of theflexible tubing and having a first magnet therein. The electrodeassembly further includes an electrically conductive tip electrode andan electrically nonconductive coupler which is connected between the tipelectrode and the distal end of the flexible tubing. The coupler and thetip electrode are coupled by an interlocking connection. The catheteralso includes a second magnet spaced from the electrode assembly along alongitudinal axis of the tubing. The first magnet and the second magnetare responsive to an external magnetic field to selectively position andguide the electrode assembly within a body of a patient.

In another embodiment, a catheter is provided that includes an electrodeassembly attached to the distal end of the flexible tubing and includinga first magnet therein. The electrode assembly including an electricallyconductive tip electrode and an electrically nonconductive coupler whichis connected between the tip electrode and the distal end of theflexible tubing. The catheter further includes a second magnet spacedfrom the electrode assembly along a longitudinal axis of the tubing. Theflexible tubing is a unitary tubing, and the second magnet is placedinside the flexible tubing after the unitary flexible tubing is formed.The first magnet and the second magnet are responsive to an externalmagnetic field to selectively position and guide the electrode assemblywithin a body of a patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first exemplary magnetic guided catheter.

FIG. 2 is a magnified view of a distal end portion of the catheter shownin FIG. 1.

FIG. 3 is a cross sectional view of the distal end portion shown in FIG.2.

FIG. 4 is a magnified cross sectional view of the electrode tip assemblyshown in FIGS. 2 and 3.

FIG. 5 is an exploded view of the distal end portion shown in FIG. 2 ofthe catheter shown in FIG. 1.

FIG. 6 illustrates an enlarged view of an alternate connecting structurefor the attachment of the tube portions to the magnets.

FIG. 7 illustrates a second exemplary embodiment of a magnetically guidecatheter.

FIG. 8 illustrates an electrode assembly for the catheter shown in FIG.7.

FIG. 9 is a magnified assembly view of a portion of the tip assemblyshown in FIG. 8.

FIG. 10 illustrates a magnet assembly for the catheter shown in FIG. 7.

FIG. 11 illustrates a distal portion of the catheter shown in FIG. 7 inan operating position.

FIG. 12 illustrates a third exemplary embodiment of a distal portion ofa magnetically guided catheter including a flexible tip and cylindricalmagnets.

FIG. 13 illustrates an exemplary manufacturing process for themagnetically guided catheter.

DETAILED DESCRIPTION OF THE INVENTION

Many specific details of certain embodiments of the invention are setforth in the following description in order to provide a thoroughunderstanding of such embodiments. One skilled in the art, however, willunderstand that the present invention may have additional embodiments,or that the present invention may be practiced without several of thedetails described in the following description.

FIG. 1 illustrates a first exemplary non-steerable, single-usemagnetically guided catheter 100 generally including a flexible outertube, or tubing, 102, a tip assembly 104, positioning magnets 106 and108 separately provided from and spaced from tip assembly 104, a Yconnector 110, a luer device 112, and an electrical connector 114. Luerdevice 112 is used to open or close a flow path so that fluid is passedthrough Y-connector 110 and tubing 102 to tip assembly 104 forirrigation purposes. Electrical connector 114 establishes electricalconnection with a power source (not shown) that operates electrodes oftip assembly 104 to perform, for example, ablation procedures, mappingor pacing procedures, or to perform other aspects of a medicalprocedure.

Although it will become evident that aspects of exemplary catheter 100are applicable to a variety of medical procedures and end uses, theinvention will be described principally in the context of a specificexample of a magnetically guided catheter. Specifically, catheter 100,as shown in FIG. 1, is believed to be particularly advantageous as anablation catheter for creating endocardial lesions during cardiacablation procedures to treat arrhythmias, and also for cardiacelectrophysiological mapping and delivering diagnostic pacing stimuli.However, the invention and the appended claims are not intended to belimited to any specific example, including but not limited to specificexamples or embodiments described herein, except when explicitly definedas such in the appended claims.

Y-connector 110 separates an inner tube 116 from electrical lead wires(not shown) extending between tip assembly 104 and electrical connector114. More specifically, tube 116 and the lead wires forward ofY-connector 110 pass internally through outer tube 102, while aft ofY-connector 110, inner tube 116 and leads for the lead wires are exposedand separated for connection to a fluid source (not shown) and the powersource, respectively. In one embodiment, electrical connector 114 is aknown connector configured to engage the power source or a power supplywith, for example, a plug-in connection. One suitable electricalconnector is a 14 pin REDEL® plastic connector commercially availablefrom LEMO of Rohnert Park, Calif., although other connectors fromvarious manufacturers may likewise be utilized.

Outer tube 102 includes a proximal end 118 coupled to Y-connector 110, adistal end 120 coupled to tip assembly 104, and an axial lengthextending between proximal end 118 and distal end 120. In oneembodiment, flexible tubing 102 is fabricated according to knownprocesses, such as extrusion processes, from any suitable tubingmaterial known in the art of medical instruments, such as engineerednylon resins and plastics, including but not limited to PEBAX® tubing ofAto Fina Chemicals, France.

In an exemplary embodiment tubing 102 is fabricated from a first tubingmaterial defining a first portion 122 of tubing 102 between Y connector110 and magnet 108, a second tubing material defining a second portion124 of tubing 102 between magnet 106 and magnet 108, and a third tubingmaterial defining a third portion 126 of tubing 102 extending betweenmagnet 106 and tip assembly 104. In an exemplary embodiment, firstportion 122, second portion 124 and/or third portion 126 are fabricatedfrom different materials and grades of materials for enhancedperformance of tubing 102 in use of catheter assembly 100. Tubing 102,by virtue of portions 122, 124, and 126 having varying flexibleproperties, is sometimes referred to as a multi-flexible tube.

For example, in one embodiment, the first material defining firstportion 122 of tubing 102 is a comparatively rigid and kink resistantbraided material. First portion 122 is formed with different portions ofbraided material, semi-soft material, and soft material fused to oneanother so that first portion 122 becomes increasingly flexible alongthe axial length as first portion 122 approaches magnet 108. The secondmaterial defining second portion 124 of tubing 102, and the thirdmaterial defining third portion 126 of tubing 102 is a soft and flexiblematerial having approximately equal flexible properties. In theillustrated embodiment, each of tubing portions 122, 124, and 126between tip assembly 104 and magnets 106 and 108 share a common outsidediameter of, for example, 7 French, although in other embodiments,tubing portions 122, 124 and 126 have varied diameters.

As shown in FIG. 1, first portion 122 extends for a majority of theaxial length of tubing 102 between proximal end 118 and distal end 120.Second portion 124 of tubing 102 extends for a shorter length than thelength of first portion 122, and third portion 126 of tubing 102 extendsfor a length that is shorter than the length of second portion 124. Byway of example only, in a specific embodiment first portion 122 extendsfor an axial length of about 126.3 cm, second portion 124 extends for anaxial length of about 2.2 cm, and third portion 126 extends for an axiallength of about 0.8 cm, although other relative lengths of the tubeportions may likewise be employed in other embodiments. The differentrelative lengths of tube portions 122, 124 and 126, as well as thedifferent flexible properties of tube portions 122, 124 and 126, allowtip assembly 104 to be more precisely positioned within a patient'sbody, while also avoiding problems of kinks and excessive deflection oftubing 102 along the majority of its length during use and handling.

As another consequence of tubing sections 124 and 126 having an unequallength, magnet 106 is spaced a first distance from tip assembly 104, andmagnet 108 is spaced a second, greater distance from magnet 106 sincetubing portion 124 is longer than tubing portion 126. Due to the spacingof magnets 106 and 108 relative to one another and also to tip assembly104, which as explained below also includes a positioning magnet (notshown in FIG. 1), the spacing of magnets 106 and 108 permits positioningadjustment of tip assembly 104 in response to variations in anexternally applied magnetic field that may otherwise not be possible, ifmagnets 106 and 108 were provided in an equal or uniform spaced relationto one another. It is contemplated, however, that in another embodimenttip assembly 104, magnet 106 and magnet 108 are equally spaced from oneanother.

In operation, a distal end portion 128 of catheter 100 including tipassembly 104 is navigated to a site in the body where a medicalprocedure, such as an atrial mapping, pacing and/or ablation are tooccur. Distal end portion 128 may extend, for example, into a heartchamber of a patient. Once distal end portion 128 is in the heartchamber, a magnetic field is applied to provide an orienting force todistal end portion 128, causing the tip positioning magnet and magnets106 and 108 to respond to the applied magnetic field and flex tubingportions 124 and 122 to precisely position tip assembly 104 forperformance of the procedure at a specific location. The magnetic fieldsused to orient tip assembly 104 are, in one embodiment, generated with amagnetic stereotactic system (not shown). Such stereotactic systems areknown and are commercially available from, for example, Stereotaxis ofSt. Louis, Mo. Such systems may include movable source magnets outsidethe body of the patient, and operative details of such systems aredisclosed in, for example, U.S. Pat. Nos. 6,475,223 and 6,755,816, thedisclosures of which are hereby incorporated by reference in theirentirety. While catheter 100 is advantageous for use with a stereotacticsystem, it is contemplated that magnetic fields and gradients to deflectcatheter tip assembly 104 may alternatively be generated by othersystems and techniques if desired.

FIG. 2 is a magnified view of distal end portion 128 of catheter 100shown in FIG. 1. Tip assembly 104 is coupled to a first end 130 of tubeportion 126 and magnet 106 is coupled to a second end 132 of tubeportion 126. A first end 134 of tube portion 124 is coupled to magnet106 and a second end 136 of tube portion 124 is coupled to magnet 108. Afirst end 138 of tube portion 122 is coupled to magnet 108, and a secondend (not shown in FIG. 2) of tube portion 122 is coupled to connector110 (shown in FIG. 1). As shown in FIG. 2, tip assembly 104 includesirrigation ports or openings 140 for passage of fluid from within tubing102 (shown in FIG. 1) to an exterior of tip assembly 104 when located inthe body of a patient.

FIG. 3 is a cross sectional view of distal end portion 128 wherein innertube 116 defines a central lumen 142 extending through each tube portion122, 124, and 126, and also through central bores formed in magnets 106and 108. Inner tube 116 has an outer diameter that is smaller than aninner diameter of tubing 102 and its portions 122, 124, and 126 suchthat space extends between an outer surface of inner tube 116 and aninner surface of tubing 102. In one embodiment, this space is used toaccommodate lead wires for electrical components of tip assembly 104.

Tip assembly 104 also includes a positioning magnet 144 having aninternal bore 146 passing therethrough. Inner tube 116 passes throughcentral bore 146 in magnet 144. Central lumen 142 is in fluidcommunication with luer 112 (shown in FIG. 1) on one end and withirrigation ports 140 extending through tip assembly 104 at the otherend. Thus, an irrigation fluid, such as saline, may be injected throughdistal end portion 128. Inner tube 116 may be, for example, a braidedpolyimide tube that maintains the flowpath through lumen 142 in allorientations of tip assembly 104, without compromising the flexibilityof tubing 102.

FIG. 4 is a magnified cross sectional view of tip assembly 104. In anexemplary embodiment tip assembly 104 includes a tip electrode 150, acoupler 152, a band electrode 154, positioning magnet 144, and atemperature sensor 156. Lead wires 158, 160 extend to tip electrode 150,and to band electrode 154 on first respective ends 162, 164 thereof, andto connector 114 (shown in FIG. 1) on second ends (not shown) so thatelectrodes 150 and 154 may be energized by a power source (not shown).

In the exemplary embodiment, tip electrode 150 may be, for example an 8Fr hemispherical-shaped tip electrode that is 2 mm in length. In otherembodiments, other sizes of tip electrodes may be utilized, includingbut not limited to 4 mm or 8 mm tip electrodes. Tip electrode 150 isformed with a plurality of openings that form irrigation ports 140 forsaline irrigation. In the exemplary embodiment, tip electrode 150 isfabricated from 90% platinum and 10% iridium, or other materials knownin the art such that tip electrode 150 is viewable under fluoroscopicexposure. While formed as an integral unit, tip electrode 150 mayinclude multiple electrode elements, such as ring electrodes forelectrophysiological mapping purposes, spaced from one another bydielectric materials as is known in the art.

Coupler 152 is a generally cylindrical, electrically nonconductivemember. It is typically made of a polymer such as PEEK™, which isrelatively rigid compared to rubber and has a limited amount offlexibility and resiliency to form a snap-fit connection, for example.Tip electrode 150 is formed with an annular projection 166 on its outersurface that engages a groove 168 within a first end 170 of coupler 152to form a snap-fit, interlocking connection. Alternatively, any matingconfiguration of tip assembly 104 and coupler 152 may be used. Coupler152 includes a second end 172 that is fitted within first end 130 oftube portion 126. Additionally, or alternatively thereto, first end 170of coupler 152 is adhered to tip electrode 150. Second end 172 ofcoupler 152 is adhered to the inner diameter of tube portion 126. Heatshrink techniques or adhesives may also be utilized to permanentlyattach coupler 152 to tube portion 126 and/or tip electrode 150.Positioning magnet 144 is disposed in a cavity which is formed at leastpartially inside the coupler 152 and which may be formed partiallyinside coupler 152 and partially inside tip electrode 150. Coupler 152houses positioning magnet 144 in tip assembly 104 and supports optionalband electrode 154, is more rigid than flexible tubing 102, and providesa convenient and reliable connection between tip electrode 150 and thirdportion 126 of flexible tubing 102.

Band electrode 154 is, in one embodiment, an 8 Fr ring-shaped bandelectrode that is for example, 2 mm in length, and spaced from tipelectrode 150 by a predetermined distance of 2 mm. Band electrode 154is, in one embodiment, fabricated from the same material as or adifferent material from tip electrode 150 and is attached to an outersurface of coupler 152.

In one embodiment, tip positioning magnet 144 is a generally cylindricalshaped permanent magnet fabricated from a known magnetic material, suchas neodymium-iron boron-45 (NdFeB-45). Alternatively, magnet 144 isformed from other materials and may have shapes different from theelongated cylindrical shape illustrated.

As shown in FIG. 4, magnet 144 includes an axially extending recess, orgroove, 176 formed into an exterior of magnet 144. Lead wires 158, 160,and a lead wire 178 for temperature sensor 158 pass through recess 176in a space defined by recess 176 and an inner surface of coupler 152.Temperature sensor 158 is, in one embodiment, a thermocouple typetemperature sensor, and lead wires 158, 160, and 178 are, for example,38 AWG wires having quad polyimide insulation.

Tip assembly 104 is particularly suited for ablation procedures whereinelectrodes 150 and 154 are energized to deliver radio frequency waves atthe site of an abnormal electrical pathway in the body. Radiofrequency(RF) energy may therefore be applied to biological tissue in proximityto tip assembly 104. Ablation procedures are typically used, forexample, within the interior chambers of the heart to thermally ablatecardiac tissue. Electrodes 150 and 154 may additionally be operated torecord intracardiac signals and to provide pacing signals.

FIG. 5 is an exploded view of catheter distal end portion 128 (shown inFIG. 1). Magnets 106 and 108 are each permanent magnets formed from, forexample, neodymium-iron boron-45 (NdFeB-45) into an elongated tubularshape.

As shown in FIG. 5, second end 132 of tube portion 126, first and secondends 134, 136 of tube portion 124, and first end 138 of tube portion 122are formed into outwardly flared sockets 182, 184, 186 and 188. Magnet106 is received in socket 182 of tube second end 132 and socket 184 oftube portion first end 134. Magnet 108 is received in socket 186 of tubeportion second end 136 and socket 188 of tube portion first end 138. Inthe exemplary embodiment, sockets 182, 184, 186, and 188 are formed witha flaring tool and extend, for example, an axial length of about 2.5 mm.Sockets 182, 184, 186, and 188 are, in the exemplary embodiment, adheredto magnets 106 and 108, respectively, and heat shrunk to fuse sockets182 and 184 to magnet 106 and sockets 186 and 188 to magnet 108. Inanother embodiment, sockets 182, 184, 186, and 188 are maintained inposition with a friction fit. In the exemplary embodiment, adjacent tubeends 132 and 134 as well as adjacent tube ends 136 and 138 contact eachother and, in a particular embodiment, are fused to each other.

Tube portions 122, 124, and 126 have an outer diameter, at locationsother than sockets 182, 184, 186, and 188, that is smaller than theouter diameter of tube portions 122, 124, and 126 at the location ofsockets 182, 184, 186, and 188. In one embodiment, the outer diameter ofmagnets 106 and 108 is the same as, or larger than, the outer diameterof tube portions 122, 124, and 126 at locations other than sockets 182,184, 186, and 188. The larger diameter magnets are able to provide anenhanced response for positioning of catheter 100 (shown in FIG. 1) withexternally applied magnetic fields.

FIG. 6 illustrates an enlarged view of an alternate connecting structurefor the attachment of tube portions 126 and 124 to magnet 106. As shownin FIG. 6, a sleeve member 190 extends over sockets 182 and 184 andforms a smooth outer surface for a transition 192 from tube portion 126over magnet 106 to tube portion 124. Sheath 190 is, in one embodiment,fabricated from a thin tube of a polyimide material, or any othermaterial that provides a low coefficient of friction.

Although only three tube portions 122, 124, and 126 and two magnets 106and 108 spaced from tip assembly 104 are shown in FIGS. 1-6, it shouldbe understood that fewer than, or more than three tube portions and twomagnets could be used without departing from the spirit of thehereinabove described catheter.

FIGS. 7 through 11 illustrate a second exemplary embodiment of amagnetically guided catheter 200 that is similar in many aspects tocatheter 100 described above. Like components and features of catheter100 are indicated with like reference numbers in FIGS. 7 through 11.Unlike catheter 100, catheter 200 includes a distal end portion 202 thatis different from tip assembly 104 described above. Distal end portion202 includes magnets 204 and 206 (instead of magnets 106 and 108),rounded tip electrode 208, and tip element 210.

FIG. 8 illustrates distal end portion 202 including a tip assembly 212that includes rounded tip electrode 208 and tip element 210. Tip element210 is a flexible member that allows tip assembly 212 to flex, bend ordeflect along its axial length to, for example, different operatingpositions 214 and 216 (shown in phantom in FIG. 8) in addition to thein-line configuration shown in solid lines in FIG. 8 wherein the tip isstraight and generally linear along a longitudinal axis 218.

Tip assembly 212 also includes a coupler 220 that joins tip element 210to tube portion 126, a band electrode 154, and a positioning magnet 222provided internal to tip assembly 212. In the exemplary embodiment, tipelectrode 208 may be, for example an 8 Fr hemispherical-shaped tipelectrode that is 2 mm in length. In other embodiments, other sizes oftip electrodes may be utilized, including but not limited to 4 mm or 8mm tip electrodes. Tip electrode 208 is formed with a plurality ofopenings that form irrigation ports 224 for saline irrigation. In theexemplary embodiment, tip electrode 208 is fabricated from 90% platinumand 10% iridium, or other materials known in the art such that tipelectrode 208 is viewable under fluoroscopic exposure. While formed asan integral unit, tip electrode 150 may include multiple electrodeelements, such as ring electrodes for electrophysiological mappingpurposes, spaced from one another by dielectric materials as is known inthe art.

Coupler 220 is a generally cylindrical, electrically nonconductivemember. It is typically made of a polymer such as PEEK™, which isrelatively rigid compared to rubber and has a limited amount offlexibility and resiliency to form a snap-fit connection, for example.Coupler 220 is connected at a first end 226 to tip element 210 and at asecond end 228 to first end 130 of tube portion 126. Coupler 220 is, inone embodiment, engaged to tip element 210 with a snap-fit, interlockingengagement similar to coupler 152 in FIG. 4. Additionally, oralternatively thereto, coupler 220 is adhered to tip element 210. Inaddition, coupler 220 is adhered to an inner section of tube portion126. Heat shrink techniques may also be utilized to permanently attachcoupler 220 to tube portion 126 and/or tip element 210. Positioningmagnet 222 is disposed in a cavity which is formed at least partiallyinside coupler 220 and which may be formed partially inside coupler 220and partially inside tip element 210. Coupler 220 houses positioningmagnet 222 in tip assembly 212 and supports optional band electrode 154,is more rigid than flexible tubing 102, and provides a convenient andreliable connection between tip element 210 and third portion 126 offlexible tubing 102.

Band electrode 154 is, in one embodiment, an 8 Fr ring-shaped bandelectrode that is for example, 2 mm in length, and spaced from tipelectrode 208 by a predetermined distance of 2 mm. Band electrode 154is, in one embodiment, fabricated from the same material as or adifferent material from tip electrode 150 and is attached to an outersurface of coupler 220.

In one embodiment, tip positioning magnet 222 is a generally cylindricalshaped permanent magnet fabricated from a known magnetic material, suchas neodymium-iron boron-45 (NdFeB-45). Alternatively, magnet 222 isformed from other materials and may have shapes different from theelongated cylindrical shape illustrated.

FIG. 9 illustrates exemplary tip element 210 in further detail. In theexemplary embodiment, tip element 210 is comprised of a single memberthat is formed into a helix, or spiral, and extends from tip electrode208 to coupler 220. Tip element 210 includes a helically shaped body 230having alternately spaced projections 232 extending away from body 230in opposite directions from one another along the length of the helix.That is, a first set of projections 234 extends distally, i.e., towardstip electrode 208, and a second set of projections 236 extendsproximally, i.e., away from tip electrode 208. The first set ofprojections 234 are staggered or offset from the second set ofprojections 236 such that the first set of projections 234 are offsetfrom, and positioned between, the second set of projections 236.

Recesses 238 extend between projections 232 and are complementary inshape to an outer contour of projections 232, but inversely shaped fromprojections 232. In the illustrated embodiment, projections 232, andrecesses 238, are trapezoidal in shape, although it is contemplated thatother shapes could likewise be utilized in alternative embodiments.

Tip element 210 is fabricated such that projections 232 from one sectionof body 230 extend into, and are captured within, recesses 238 from anadjacent section of body 230 to form an interlocking arrangement. Due toprojections 232 being complementary in shape to recesses 238 and thusdefining sockets or compartments for projections 232, projections 232are movable only a defined distance within recesses 238. In particular,and as shown in FIG. 9, tip element 210 is positionable to create aspace or gap 240 between leading edges of projections 232 and inneredges of recesses 238. Projections 232 and recesses 238 of tip element210 extend completely along the length of body 230 and, in oneembodiment, are uniformly spaced and sized around a perimeter of body230. Alternatively, projections 232 and recesses 238 may be differentlysized and/or spaced around the perimeter of body 230.

As a consequence of gaps 240, and also the complementary shapes ofprojections 232 and recesses 238, projections 232 are provided a freedomof movement within recesses 254 without being able to be removedtherefrom. Accordingly, sections of tip element 210 can move toward andaway from each other a defined distance to decrease and increase,respectively, gaps 240. It is thus possible for sections of tip element210 to move relative to one another in multiple ways. For example, tipelement 210 may be compressed so that all of gaps 240 are closed, ornearly closed, to reduce the longitudinal length of tip assembly 202 bythe cumulative dimensions of gaps 240 along a longitudinal axis 242.Additionally, sections of tip element 210 may exhibit cascaded orsequential movement along longitudinal axis 242 wherein some gaps 240are closed along longitudinal axis 242 while other gaps remain open,either partially or fully. This allows gaps 240 between any adjacentsections of tip element 210 to be opened or closed in an uneven ornon-uniform manner. As such, gaps 240 on one side of tip assembly 202may be closed while gaps 240 on the other side of tip assembly 202 maybe opened. The result of this configuration is that tip assembly 202curves in the direction of the closed gaps 240 and away from thedirection of the opened gaps 240. It can be appreciated that movement invertical and horizontal planes may simultaneously occur due to theinterlocking construction of tip element 210 to flex and deflect tipassembly 202 to a practically unlimited number of positions. Tipassembly 202 may deflect in the manner described due to, for example,impact forces on an outer surface of tip assembly 202 in use, and mayalso, in whole or in part, be the result of the magnetic response ofpositioning magnet 222 (shown in FIG. 8) and magnets 204 and 206 (shownin FIG. 7).

In an exemplary embodiment, tip element 210 is laser cut from a materialsuitable for surgical use, such as an electrically conductive,non-corrosive material. In one exemplary embodiment, the material isplatinum. In another exemplary embodiment, the material is stainlesssteel. Projections 232 and recesses 238 of tip element 210 are, in theexemplary embodiment, laser cut out of a cylindrical piece of material.It should be evident that as the number of helices increases in tipelement 210, the flexing capability also increases. In addition, as thepitch of the helix decreases, the ability of tip element 210 to moverelative to itself increases. The flexibility may further be adjusted byproviding different numbers and shapes of projections and recesses toproduce tip assemblies that flex to varying degrees to meet differentobjectives. The combination of the multi-flexing tubing previouslydescribed and independent flexing of the tip assembly 212 isparticularly advantageous for certain applications. For example, RFenergy may be more specifically targeted to desired tissue areas forablation procedures when tip element 212 is flexed than when it is notflexed, and provides a physician with additional positioning capabilityover conventional catheter devices.

In an alternative embodiment, tip assembly includes a plurality ofadjacent rings that extend along longitudinal axis 242. Each ring has adistal side and a proximal side and each side includes alternatingprojections and recesses. This structure provides for flexibility in amanner that is similar to the exemplary embodiment described above. Insuch a configuration, the rings are constructed substantiallyidentically to each other.

Tip assembly 212 is particularly suited for ablation procedures whereinelectrode 208 is energized to deliver radio frequency waves at the siteof an abnormal electrical pathway in the body. Radiofrequency (RF)energy may therefore be applied to biological tissue in proximity to tipassembly 212. Ablation procedures are typically used, for example,within the interior chambers of the heart to thermally ablate cardiactissue. Electrode 208 may additionally be operated to recordintracardiac signals and to provide pacing signals. It should be notedthat tip assembly 212 is also suited for recording of intracardiacsignals and to provide pacing signals. While formed as an integral unit,tip electrode 208 may include multiple electrode elements, such as ringelectrodes for electrophysiological mapping purposes, spaced from oneanother by dielectric materials as is known in the art.

FIG. 10 illustrates a magnet assembly 244 for catheter 200 (shown inFIG. 7). Unlike magnets 106 and 108 (shown in FIG. 1) that arecylindrical in shape and have a constant outer diameter, magnet 204 isoutwardly flared and has a generally ellipsoidal contour. That is, theouter diameter of magnet 204 is largest at an axial midpoint 246 anddecreases from midpoint 246 to opposing ends 248, 250 of magnet 204,providing magnet 204 with a curved profile along an axial length ofmagnet 204.

In one embodiment, magnet 204 is encapsulated in sockets formed intoadjacent tube portions as described above. Alternatively, magnet 204 isencapsulated in a sleeve that extends from the tube portions to covermagnet 204. Similarly to magnets 106 and 108, magnet 204 includes acentral bore through which a tube passes. Magnet 204 is formed from, forexample, neodymium-iron boron-45 (NdFeB-45) into the illustrated shapeor an alternative shape. It should be understood that magnet 206 (shownin FIG. 7) may be formed in the same shape as or a different shape frommagnet 204.

FIG. 11 illustrates a distal portion of catheter 200 in an exemplaryoperating position that shows the deflection of tip assembly 212 andmagnets 204 and 206. By applying magnetic fields to magnets 204 and 206,and also positioning magnet 222 (shown in FIG. 7), the distal portion ofcatheter 200 may be precisely positioned at a specific location withinthe patient's body. The magnetic fields may be generated and controlledby, for example, a magnetic stereotactic system (not shown).

FIG. 12 illustrates a distal portion of an alternative catheter, such asa catheter 260. As illustrated, a distal portion of catheter 260 isshown in an exemplary operating position in which the deflection iscaused by tip assembly 212 and magnets 106 and 108. By applying magneticfields to magnets 106 and 108, and also positioning magnet 222 (shown inFIG. 7), the distal portion of catheter 260 may be precisely positionedat a specific location within the patient's body. The magnetic fieldsmay be generated and controlled by, for example, a magnetic stereotacticsystem (not shown).

The external positioning magnets of catheters 100, 200, and 260 arebelieved to provide manufacturing benefits, and also performancebenefits, in relation to conventional, and more complicated, catheterconstructions for use with stereotactic systems. Larger positioningmagnets are provided for increased magnetic response and performance,and tubing is used that is generally smaller in internal diameter thanthe magnets, thereby resulting in material savings in comparison toknown catheters having larger tubing to accommodate the magnets. Inaddition, increased flexibility is provided. Sockets in the tubesencapsulate the external positioning magnets in a very manufacturableand generally low cost construction. The external positioning magnetsthat are separately provided from the electrode tips also reduce acomplexity and parts count in the tip assembly relative to other knowncatheter tips providing comparable functionality.

FIG. 13 illustrates an exemplary manufacturing process for the magneticguided catheter. Tubing 102 is a unitary tubing that is unitary inconstruction and formed as a single tubing prior to placing the magnetsinside. In an exemplary embodiment, magnets 106 and 108 may be pushedinto tubing 102 during the manufacture process in the directionillustrated by arrow 103. For example, magnets 106 and 108 may bepositioned on mandrels 101 and 105, respectively, and pushed into tubing102 one at a time using a lubricant such as, alcohol, to facilitatereceiving magnets 106 and 108 therein. The alcohol convenientlyevaporates after a short time. Magnets 106 and 108 are shown mounted onmandrels 101 and 105 outside of tubing 102. Magnets 106 and 108 areinserted into tubing 102 one at a time, by pushing mandrels 101 and 105separately and sequentially in the direction of arrow 103.

According to this method, there may exist an interference fit betweenmagnets 106 and 108, and tubing 102, thereby securing the position ofmagnets 106 and 108. It is noted that the drawings are exaggerated tobetter illustrate the interference fit. In reality, the interference fitmay not be as pronounced as it is shown in the drawings. Theinterference fit may be formed by an outer diameter of the at least onemagnet being larger than an inner diameter of the unitary flexibletubing. For example, the interference fit may be formed by magnets 106and 108 having an outer diameter about 0.005 inches larger than theinner diameter of tubing 102.

In another exemplary embodiment, magnets 106 and 108 may be pushed intotubing 102 without any interference fittings. In this embodiment, tubing102 may be wrapped in heat-shrink film or heat-shrink tubing. Theheat-shrink process shrinks the heat-shrink film or tubing around tubing102 so that the position of magnets 106 and 108 is secured within tubing102.

Heat-shrink processes are well understood in the arts. For purposes ofdiscussion, however, the process may implement any of a wide variety ofcommercially available heat shrink film or tubing. Magnets 106 and 108are first positioned within the heat shrink tubing. The magnets arereadily positioned while the heat shrink tubing is in an initial state(e.g., at room temperature) prior to processing. Optionally, the magnetmay be pretreated with a coating, e.g., to reduce the effects ofcorrosion. Application of heat to the heat shrink film or tubing shrinksthe film or tubing around magnets 106 and 108. Shrinkage of the tubingaround the magnet applies the necessary pressure to maintain magnets 106and 108 in the desired position within tubing 102 after the heat shrinkfilm or tubing cools.

Also in exemplary embodiments, catheter 100 can be constructed to havedifferent flexibilities along the length of tubing 102, particularly inthe distal region where the magnets are placed. Typically, portion 126(shown in FIG. 1) between the distal end (where the tip electrode islocated) and first magnet 106 is desired to be the most flexible.Portion 124 between first magnet 106 and second magnet 108 disposedproximally from first magnet 106 is desired to have less flexibility.Still additional portions and additional magnets may be provided, withthe proximal portions having less and less flexibility.

The flexibility can be determined by material properties and/orthickness. Thus, unitary tubing 102 can be made to have varying materialproperties along its length toward the distal end, so that the differentportions will have different flexibilities. The shaft can also decreasein thickness toward the distal end. A thinner wall of tubing 102 resultsin greater flexibility, while a thicker wall of tubing 102 results inless flexibility.

Flexibility can change either continuously/gradually or in abrupt stepsbetween the portions. The abrupt steps may be useful in defining thelocations of the magnets, especially in the embodiment where the magnetsare pushed into the shaft with a lubricant. As magnets 106 and 108 passthrough different flexibility zones defined by abrupt steps, the abruptchange in flexibility provides tactile feedback that magnets 106 and 108are passing from one flexibility zone to another.

The unitary construction of the flexible tubings of catheters 100 and200 is believed to provide manufacturing benefits, and also performancebenefits, in relation to conventional, and more complicated, catheterconstructions for use with stereotactic systems. The catheter can bemanufactured without requiring magnet-shaft fusion and without joints,ensuring high reliability and safety of the catheter. The unitary tubingis easier to manufacture, takes less time to manufacture, and does notrequire an expensive and complicated fusion machine. Eliminating thejunction of the magnet and the shaft also reduces or altogethereliminates undesirable stiffness. In addition, the magnets that areseparately provided from the electrode tips also reduces complexity andparts count in the tip assembly relative to other known catheter tipsproviding comparable functionality. The unitary flexible tubing mayextend along substantially the entire length of the catheter body, andmay have a distal end to be coupled to an electrode assembly and aproximal end to be coupled to a handle. Alternatively, the unitaryflexible tubing may extend along a portion of the catheter body with nofused connections between the magnets, but may be attached to additionalcomponents to form the entire length of the catheter body. For example,the unitary flexible tubing containing the magnets with no fusedconnections may be fused with another flexible tubing to form the entirelength of the catheter body.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

What is claimed is:
 1. A catheter comprising: an elongate flexible member; a longitudinal axis; a tip assembly including a proximal end and an electrically conductive electrode; an electrically nonconductive material connecting a distal portion of the elongate flexible member to the tip assembly; a first magnet having a distal end and a proximal end, the first magnet distal end spaced proximally from the proximal end of the tip assembly along the longitudinal axis by a first distance, wherein no magnet is positioned between the first magnet and the tip assembly proximal end; and a second magnet spaced from the first magnet along the longitudinal axis by a second distance, the second distance greater than the first distance, wherein the first magnet and the second magnet are responsive to an external magnetic field to selectively position and guide the electrode assembly within a body of a patient, and wherein no magnet is positioned between the first magnet and the second magnet.
 2. The catheter in accordance with claim 1, wherein the electrically nonconductive material includes a band electrode on an external surface thereof, the band electrode spaced from the electrically conductive electrode.
 3. The catheter in accordance with claim 1, wherein the second magnet has one of a cylindrical shape and an ellipsoidal shape.
 4. The catheter in accordance with claim 1, wherein a portion of the flexible member distal to the second magnet is more flexible than another portion of the flexible member proximal to the second magnet.
 5. The catheter in accordance with claim 4, wherein the portion of the flexible member distal to the second magnet is thinner than the portion of the flexible tubing member proximal to the second magnet.
 6. The catheter in accordance with claim 1, further comprising a lumen passing through the first magnet and the second magnet, and in fluid communication with the tip assembly, wherein the tip assembly has at least one irrigation port.
 7. A catheter comprising: an elongate flexible member including a first portion having a length; an electrode assembly including a flexible, electrically conductive electrode comprising a longitudinal axis and a sidewall, wherein the sidewall is defined by a member extending about the longitudinal axis, the member including a first plurality of projections extending toward an adjacent section of the member; a first magnet, wherein the electrode assembly further includes at least a portion of the first magnet, and wherein the first magnet is spaced from a distal tip of the catheter along the longitudinal axis; an electrically nonconductive material connecting a distal portion of the elongate flexible member to the electrode assembly; a second magnet spaced from the first magnet by the elongate flexible member first portion, wherein the first magnet and the second magnet are responsive to an external magnetic field to selectively position and guide the electrode assembly within a body of a patient; and a third magnet separated from the second magnet by a first distance, wherein the first distance is greater than the length of the elongate flexible member first portion, and wherein no magnet is positioned between the second magnet and the third magnet.
 8. The catheter in accordance with claim 7, wherein the first plurality of projections form an interlocking arrangement with a second set of projections extending from an adjacent section of the member.
 9. The catheter in accordance with claim 7, wherein the first plurality of projections form a first plurality of recesses that are complimentary in shape to the second plurality of projections.
 10. The catheter in accordance with claim 7, wherein the sidewall is a substantially cylindrical sidewall provided with at least one elongate gap formed in the wall to provide a freedom of movement and shortening of a length of the electrode under an applied force.
 11. The catheter in accordance with claim 7, wherein the sidewall comprises alternating interlocking blocks disposed on opposite sides of an elongate gap, each block having a head and a neck, and the head being wider than the neck.
 12. The catheter in accordance with claim 7, further comprising a lumen passing through the first magnet and the second magnet, and in fluid communication with the electrode assembly, wherein the electrode assembly has at least one irrigation port.
 13. A catheter comprising: an elongate flexible member; an electrode assembly including an electrically conductive electrode; an electrically nonconductive material connecting a distal portion of the elongate flexible member to the electrode assembly; a first magnet, wherein the electrode assembly further includes at least a portion of the first magnet, and wherein the first magnet is spaced from a distal tip of the catheter along the longitudinal axis; a second magnet spaced from the electrode assembly by a first distance, wherein the first magnet and the second magnet are responsive to an external magnetic field to selectively position and guide the electrode assembly within a body of a patient; and a third magnet separated from the second magnet by a second distance, wherein the second distance is greater than the first distance, and wherein no magnet is positioned between the second magnet and the third magnet.
 14. The catheter in accordance with claim 13, wherein a portion of the flexible member distal to the second magnet is thinner than a portion of the flexible member proximal to the second magnet.
 15. The catheter in accordance with claim 13, wherein a portion of the flexible member distal to the second magnet includes a material which is more flexible than a different material in a portion of the flexible member proximal to the second magnet.
 16. The catheter in accordance with claim 13, wherein the electrode comprises a substantially cylindrical sidewall provided with at least one elongate gap selected from the group consisting of an annular gap around a portion of a circumference of the sidewall and a helical gap forming a helical pattern on the sidewall.
 17. The catheter in accordance with claim 13, wherein the electrode comprises a substantially cylindrical sidewall provided with at least one elongate gap formed in the sidewall to provide a freedom of movement and shortening of a length of the electrode under an applied force.
 18. The catheter in accordance with claim 13, wherein the electrode comprises alternating interlocking blocks disposed on opposite sides of an elongate gap, each block having a head and a neck, and the head being wider than the neck.
 19. The catheter in accordance with claim 13, wherein the electrically nonconductive material includes a band electrode on an external surface thereof, the band electrode spaced from the electrically conductive electrode.
 20. The catheter in accordance with claim 13, further comprising a lumen passing through the first magnet and the second magnet, and in fluid communication with the electrode assembly, wherein the electrode assembly has at least one irrigation port. 